Hynobius tsurugiensis, Tominaga & Matsui & Tanabe & Nishikawa, 2019

Tominaga, Atsushi, Matsui, Masafumi, Tanabe, Shingo & Nishikawa, Kanto, 2019, A revision of Hynobius stejnegeri, a lotic breeding salamander from western Japan with a description of three new species (Amphibia, Caudata, Hynobiidae), Zootaxa 4651 (3), pp. 401-433 : 417-419

publication ID	https://doi.org/ 10.11646/zootaxa.4651.3.1
publication LSID	lsid:zoobank.org:pub:0C85653A-911A-44C6-A4BD-38F680B6199A
persistent identifier	https://treatment.plazi.org/id/EFAF1101-7018-492B-A88F-EE896135A738
taxon LSID	lsid:zoobank.org:act:EFAF1101-7018-492B-A88F-EE896135A738
treatment provided by	Plazi
scientific name	Hynobius tsurugiensis
status	sp. nov.

Treatment

Hynobius tsurugiensis sp. nov.

(Japanese name: Tsurugi-sanshou-uwo)

(English name: Tsurugi salamander)

( Figs. 7 View FIGURE 7 C–E, 8B, 9B, G–H)

H. naevius View in CoL (part, Shikoku local form): Sato 1943: 206.

H. naevius (part, sample 7 from easternmost part of Shikoku in Group B): Tominaga et al. 2005a: 921–937.

H. naevius (part, sample 8 in Group B): Tominaga et al. 2005b: 1229–1244, Fig. 6B. View FIGURE 6

H. naevius (part, sample 7, eastern Shikoku sample in Clade 4): Tominaga et al. 2006: 677–684.

H. yatsui View in CoL (part): Tominaga & Matsui 2008: 107.

H. stejnegeri View in CoL (part): Matsui et al. 2017: 538.

Holotype: T2096 ( Fig. 7C View FIGURE 7 ), an adult female from Mt. Tsurugi, Miyoshi-shi (formerly Higashiiyayama-son), Tokushima Prefecture (33 o 51’ N, 134 o 05’ E, alt. 1843 m a.s.l.) collected by S. Tanabe on 16 July 1990. GoogleMaps

Paratypes: KUHE 8335–8337 View Materials , 8341–8355 View Materials , 8357–8360 View Materials , 8362–8364 View Materials and T1238–T1240, T1243–T1244, T1247, 26 males and five females from the type locality by S. Tanabe and T. Hayashi on 21 June 1985 ; T1597, T1599– T1600, two males and one female from the type locality by S. Tanabe on 23 September 1987; T1959–T1964, four males and one female from the type locality by S. Tanabe on 6 September 1988; T2001–T2002, two males from the type locality by S. Tanabe on 17 July 1989; T2093–T2094 and T2096, two males and one female from Miyoshi-shi , by S. Tanabe on 14–16 July 1990 ; T2095, one female from Mima-shi (formerly Koyadaira-son ), Tokushima Prefecture by S. Tanabe on 15 July 1990 ; T2198, one female from the type locality by T. Nii from June to July 1991; T2873 ( Fig. 7D, E View FIGURE 7 ), one male from Mt. Maruzasa, Miyoshi-shi ; T2969, one female from the type locality by S. Tanabe on 5 September 1991 ; T3018–T3021, one male and three females from Naka-cho , Tokushima Prefecture by S. Tanabe on 18 July 2000 .

Referred specimens: KUHE 28044–28045 View Materials from Kami-shi (formerly Monobe-son), Kochi Prefecture by T. Shimada on 23 September 2000 .

Etymology: The specific name " tsurugiensis " refers to Mt. Tsurugi, the type locality of the species.

Diagnosis: A medium-sized species (adult SVL 51–72 mm in males and 59–74 mm in females) within the lotic breeding Hynobius , breeding in montane streams; dorsum maculated with large yellow; limbs and tail long; tips of fore- and hindlimbs adpressed on body never meeting (overlap of -3.0 to -0.5 costal folds in males and -3.5 to - 1.5 in females); fifth toe poorly developed; ova large, pigmentless; egg sacs short and string-like, without distinct whiptail structure on free end; morphometrically most similar to H. kuishiensis sp. nov., described below, but with larger body size, small number of upper and lower jaw teeth, and vomerine teeth, relative size to SVL in shorter fifth toe, and reddish purple or dark blue ground color with large or continuous yellow dorsal marking of their trunk and tail.

Description of holotype (measurements in mm): Head-body small ( SVL 61.1); head oval and moderately depressed, distinctly longer (HL 14.0, 22.7% SVL) than wide (HW 10.5, 17.1%); snout rounded, slightly projecting beyond lower jaw; nostril close to snout tip; labial fold absent; eye large, prominently protruded, slightly inset from edge of head in dorsal view; upper eyelid well developed ( UEW 2.1, 3.4% SVL), shorter ( UEL 3.6, 5.8% SVL) than snout (SL 4.2, 6.8% SVL); gular fold distinct, curving slightly anteriorly; parotoid gland evident, extending from angle of jaw to gular fold; postorbital grooves distinct, branching posterior to angle of jaw, one short and running down to lower jaw, the other long and posteriorly to parotoid gland; vomerine tooth series slightly wider ( VTW 2.9, 4.7% SVL) than long ( VTL 2.6, 4.2% SVL), vomerine tooth deep V-shaped, series nearly touching at midline ( Fig. 8B View FIGURE 8 ), tongue broad, both sides free from mouth floor; fore- and hindlimbs short and thick (FLL 13.6, 22.1% SVL; HLL 18.4, 29.9% SVL); number of costal grooves between axilla and groin 13; depressed limbs separated by two costal folds; relative length of fingers IV<I<III=II, toes V<I<II<IV<III; fifth toe poorly developed (5TL 0.8, 1.3% SVL); cloaca longitudinal slit; genital tubercle on anterior cloaca absent; tail short ( TAL 39.6, 69.2% SVL), cylindrical at base and middle ( BTAW 6.2, 10.0% SVL; BTAH 6.3, 9.5% SVL, MTAW 4.6, 7.1% SVL; MTAH 5.3, 8.9% SVL), slightly compressed posteriorly, caudal fin never developed; tip of tail slightly sharpened in lateral view.

Additional Measurements and counts of the holotype: IND (3.3, 5.7% SVL); IOD (3.4, 5.7% SVL); AGD (33.5, 52.1% SVL); TRL (47.6, 76.4% SVL); MXTAH (6.3,10.9% SVL); 2FL (2.7, 4.2% SVL); 3FL (2.4, 3.8% SVL); 3TL (4.3, 7.2% SVL); UJTN (54); LJTN (53); VTN (40).

Color: In life, dark brown in dorsal ground color, with continuous, yellow markings, ( Fig. 7C View FIGURE 7 ). Underside of body lighter than dorsum with white marking. In preservative, dorsal and ventral ground color tending to fade.

Variation: Morphometric data are summarized in Tables 3 View TABLE 3 and 4 View TABLE 4 . Males are slightly smaller in SVL than females. Males had slightly larger relative values in RHW (median=17.1% SVL), RLJL (14.2% SVL), RSL (6.9% SVL), RIND (5.5% SVL), RIOD (5.5% SVL), RUEL (5.7 % SVL), RTAL (72.5% SVL), RMTAH (9.8% SVL), RFLL (23.2% SVL), and RHLL (29.1% SVL) than in females (16.0, 13.6, 6.6, 5.2, 5.2, 5.4, 70.7, 8.9, 21.8, and 27.6% SVL, respectively). Males had shorter RAGD (median=52.8% SVL) and RTRL (76.7% SVL) than females (55.0 and 77.4% SVL, respectively). Third toe was usually longer than the fourth like holotype. Fifth toe was almost always present but usually poorly developed. Combined series of vomerine teeth were similar between sexes (medians of VTW / VTL =106.7% SVL in males and 105.9% SVL in females). Dorsal color and markings were usually reddish purple or dark blue ground color with bright yellow continuous markings on trunk and tail. Geographic and individual variations in color were not remarkable (Tominaga et al. 2005).

Eggs and egg sacs: The egg sac morphology of Hynobius tsurugiensis sp. nov. is shown in Fig. 9B View FIGURE 9 . Egg sacs were string-like in shape with thin envelope, and lacked a distinct whiptail structure on the free end. The clutch size was small, ranging from 19–28 (mean ± SD =22.6 ± 3.6, n = 13). The diameter of ova from one female was 6.0 mm in average (n =10) mm. Both the animal and the vegetal poles were cream in color.

Larvae: SVL and TAL of larvae (n=4) after hatching ranged from 12.4–13.0 (mean ± SD = 12.7± 0.2) mm and 8.8–10.2 (9.5± 0.8) mm, respectively. The hatched larvae had no balancers. SVL and TAL of fully grown larvae (n=3) at St. 61–63 of Iwasawa & Yamashita (1991) of the first year in late July to late August ranged from 14.6–16.1 (15.4± 0.7, n = 3) mm and 12.6–13.9 (13.1± 0.7, n = 3) mm, respectively. Head rounded in dorsal and lateral views ( Fig. 9G, H View FIGURE 9 ); snout short and broadly rounded; eyes slightly protruded, inset from edge of head in dorsal view; labial fold indistinct; external gills developed; caudal fin slightly higher than head; dorsal fin higher than ventral fin; origin of dorsal fin at half of trunk; ventral fin originating from vent; tail tip weakly pointed; limbs short but slightly robust; claws on fingers and toes absent. In life, dorsum dark brown with a few tiny white dots; venter whitish and transparent; lateral side of the trunk usually brown without markings, caudal fine transparent with small brown dots. SVL and TAL of metamorphosing juveniles (n=3) in middle of September ranged from 19.0–19.6 (19.3± 0.3) mm and 14.5–15.7 (15.1±0.6) mm, respectively.

Range: Known from mountain regions of Shikoku district, Western Japan ( Fig. 10 View FIGURE 10 ), from Mt. Tsurugi, Mt. Maruzasa, and Mt. Takashiro, Tokushima Prefecture, and Kami-shi (formerly Monobe-son) Kochi Prefecture. Hynobius tsurugiensis sp. nov. seems to be largely sympatrically distributed with H. hirosei and Onychodactylus kinneburi but allopatric from its relative, H. kuishiensis sp. nov.

Morphological Comparisons: Hynobius tsurugiensis sp. nov. is distinct from all 37 lentic breeding Hynobius species with having cylindrical tail at base and small number of large unpigmented eggs per clutch. Hynobius tsu- rugiensis sp. nov. is different from other lotic breeding Japanese congeners, including H. boulengeri , H. hirosei , H, shinichisatoi , H. ikioi , H. osumiensis , H. amakusaensis , H. kimurae , H. fossigenus , H. katoi , H. naevius , H. sematonotos , and H. oyamai by combination of the presence of continuous bright yellow dorsal markings, white ventral marking on the trunk, and smaller body size ( Matsui et al. 2004; Nishikawa & Matsui, 2014; Matsui et al. 2017; Okamiya et al. 2018; Tominaga et al. 2019). Hynobius tsurugiensis sp. nov. is similar in color to H. ikioi ( Nakamura & Uéno 1963) , but the new species has smaller body size ( SVL: 51.1–71.8 mm in males and 59.2–73.8 mm) than H. ikioi ( SVL: (69.0– 93.2 in males and 79.9–93.0 mm in females) ( Matsui et al. 2017).

Hynobius tsurugiensis sp. nov. is slightly larger (SVL= 51.1–71.8 mm in males, 59.2–73.8 mm in females) than all Taiwanese species, although ranges of SVL overlapped (adult SVL usually 50–60 mm and less than 69 mm [ Lai & Lue, 2008]). However, H. tsurugiensis sp. nov. differs in color and in longer (RHL 21.5–25.0%) and wider (RHW 15.4 –18.3 %) head and longer forelimb (RFLL=20.4–25.0%) and hindlimb (RHLL=26.3–31.4%) from all five Taiwanese species (mean RHL= 18.3–23.9%, mean RHW= 15.0–16.5%, mean RFLL= 19.1–25.0%, and mean RHLL= 22.4–28.9% [calculated from data of Lai & Lue 2008]).

Hynobius tsurugiensis sp. nov. is genetically close to H. guttatus sp. nov. from Chubu-Kinki districts but is clearly distinguished from the latter by color and size of dorsal and ventral marking, larger body size, relatively smaller head, smaller number of upper and lower jaw teeth, and vomerine teeth, and relatively shallower vomerine tooth series. Hynobius tsurugiensis sp. nov. is morphometrically similar to H. kuishiensis sp. nov. described below, also from Shikoku but is also distinguishable from the latter by color and size of dorsal and ventral marking, smaller number of upper and lower jaw teeth, and vomerine teeth. Hynobius tsurugiensis sp. nov. differs from H. stejnegeri View in CoL by color and size of dorsal and ventral marking, smaller number of upper and lower jaw teeth, and vomerine teeth, relatively lager snout and tail, and larger VTW/VTL values, and relatively shallower vomerine teeth series.

Natural history: Breeding occurs from May to June, when egg sacs are attached to stones under the ground around headwater of mountain streams. Larvae can metamorphose in early autumn without feeding like H. stejnegeri , H. guttatus sp. nov., and H. kuishiensis sp. nov.